1. Technical Field
The present invention relates to a transfer device of an electrophotographic system and an image forming apparatus.
2. Related Art
There is proposed an image forming apparatus which develops a latent image of an image carrier by a developing device, thereby obtaining a visualized image and is provided with a transfer device that directly transfers a toner image on the image carrier to a transfer material such as paper. Also, there is proposed an image forming apparatus which visualizes a latent image of an image carrier by a developing device, thereby obtaining a visualized image, transfers a toner image on the image carrier to an intermediate transfer medium that is constituted of a belt tensioned around a plurality of rollers, or a drum, and is provided with a transfer device that transfers a toner image on the intermediate transfer medium to a transfer material.
In JP-A-3-4241, there is disclosed an image forming apparatus which develops a latent image on a photoconductor as an image carrier by a developing device, thereby obtaining a toner image and is provided with a transfer drum that transfers the toner image on the photoconductor to a transfer material. The transfer drum is provided with a gripper for gripping the transfer material, an electrifier for adsorption, which adheres the transfer material to the transfer drum by electrostatic adsorption, an electrifier for transfer, which is for transferring the toner image on the photoconductor to the transfer material, and an electrifier for separating, which is for separating the transfer material with the toner image transferred thereto, from the transfer drum.
In JP-T-2000-508280, there is disclosed an image forming apparatus which develops a latent image on a photoconductor by a liquid developer, thereby forming a toner image, transfers the toner image on the photoconductor to an intermediate transfer drum as an intermediate transfer medium, and is provided with a transfer drum that transfers the toner image of the intermediate transfer drum to a transfer material. The toner image on the intermediate transfer drum is transferred to the transfer material by heating and pressurizing. Also, the transfer drum is provided with a gripper that grips the transfer material. Also, a separating member that peels off the transfer material from the transfer drum is disposed outside the transfer drum.
But, in the image forming apparatus disclosed in JP-A-3-4241, it is necessary to dispose a plurality of electrifiers such as the electrifier for adsorption of the transfer material, the electrifier for transfer, and the electrifier for separating in the transfer drum, so that a configuration of the apparatus is complicated and control of each electrifier is also difficult. Also, in the image forming apparatus disclosed in JP-T-2000-508280, since the transfer of the toner image to the transfer material is thermal transfer by heating and pressurizing, the adhesion properties of the transfer material with the toner image transferred thereto to the transfer drum becomes stronger, so that there is a problem that the separating of the transfer material from the transfer drum becomes difficult.